The present embodiments relate to a signal path for a small signal oscillation at a frequency of at least 20 GHz occurring in a magnetic resonance system.
Magnetic resonance systems have an examination volume. The examination volume is the volume, in which the static, locally essentially homogeneous basic magnetic field of the magnetic resonance system exists and to which magnetic resonance excitation pulses may be applied by the whole body coil of the magnetic resonance system. All metallic cables that run in the examination volume are to be equipped with sheath current filters in order to prevent sheath waves being induced on the cable sheaths. This practice may be known to persons skilled in the art.
Various signals occur in magnetic resonance systems. The signals are power signals such as the high-frequency magnetic resonance excitation pulses or gradient pulses, for example. The signals are also, for example, small signals such as magnetic resonance signals, control signals (e.g., for tuning circuits), and clock signals. Power signals are to be conducted via metallic conductors. Small signals are likewise initially transmitted via cables in the prior art. However, the use of radio links with or without frequency conversion for the transmission of small signals is also known.
The magnetic resonance signals may be digitized while the magnetic resonance signals are still in the local coil, and the received magnetic resonance signals may be transferred in digitized form to the control and evaluation device of the magnetic resonance system. A high bandwidth for transfer of the digitized magnetic resonance signal is provided in this case. This uses high transmission frequencies of 20 GHz and more. The problem that arises is that of how such high-frequency signals may be transferred from the local coil to the control and evaluation device.
In one approach, the signals are transferred via a corresponding high-frequency radio link. Because of the strongly distinct directional characteristic of the emitting signal, this approach is prone to problems. These problems may be resolved.
A further approach is cable-based transmission. This approach too is prone to problems. For example, planar cable structures such as striplines exhibit high losses at these high frequencies. Although hollow conductor systems exhibit lower losses, the hollow structures are however voluminous and may only be installed with mechanical difficulty. It is a complicated matter to combine the two solutions with sheath current filters known in the prior art.